title: Early effect of glucose and oxygen deprivation on the spontaneous acetylcholine release from the myenteric plexus of the guinea pig ileum.
abstract: The early effects of glucose and oxygen deprivation on the spontaneous acetylcholine output from the myenteric plexus - longitudinal muscle preparation of the guinea pig ileum were studied using an incubation chamber that permitted rapid sample collection in 2-min intervals. Glucose deprivation or hypoxia resulted in a gradual decline in rate of spontaneous acetylcholine collection in 2-min intervals. Glucose deprivation or hypoxia resulted in a gradual decline in rate of spontaneous acetylcholine output. However, glucose deprivation plus hypoxia caused an acceleration in acetylcholine output within 10-15 min, which attained a rate seven times greater than observed under normal conditions. Recovery of low resting rates was obtained by reintroduction of oxygen and glucose into the bath medium. Neither morphine (2.7 x 10(-5) M) nor tetrodotoxin (1.6 x 10(-6) M) prevented the increase in acetylcholine output induced by energy deprivation. The substitution of Ca2+ by Mg2+, in the presence of EGTA, greatly reduced the acetylcholine output induced by energy deprivation. However, a small transitory output of acetylcholine was observed under these conditions which was resistant to tetrodotoxin and ot affected by depolarizing amounts of K+. The transitory output was repeatable by reintroduction of glucose and oxygen to the Ca2+-free medium with subsequent return to conditions of hypoxia and glucose deprivation. These results suggest that energy deprivation initially stimulates normal acetylcholine secretion by (a) increasing Ca2+ influx across the plasma membrane and (b) mobilizing an intracellular Ca2+ poll. This implies that processes involved in maintenance of normal low transmitter release are more sensitive to energy lack than the neurosecretion process itself.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D005947:Glucose / Q000172:deficiency*; D006168:Guinea Pigs; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009197:Myenteric Plexus / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D013779:Tetrodotoxin; D004533:Egtazic Acid; D009020:Morphine; D008274:Magnesium; D005947:Glucose; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium